Spain has released details on the seizure by its navy of a ship in the Arabian Sea that was carrying 15 Scud missiles.

In a news conference Wednesday, Spain's defense minister, Federico Trillo, said that the Spanish Frigate Navarra and the support vessel Patino intercepted the ship, the Sosan.

Mr. Trillo said the captain of the Sosan, which was not flying a flag, refused to halt and submit to inspection. After firing warning shots, Spanish special forces boarded the ship by helicopter and by launch and seized it.

Hidden amid a shipment of cement Spanish officials found 15 Scud missiles and more than 80 drums of chemicals.

The Spanish ships had been assigned to patrol the area under a U.S.-led coalition against terrorism, known as Operation Enduring Freedom. U.S. intelligence services had been monitoring the ship since it left the North Korean port of Nampo weeks ago.

Asked about the legality of the seizure of the Sosan, Mr. Trillo pointed out that under international maritime law, any ship without a flag is a pirate ship and can be inspected by naval officials. He also said the seizure was justified under U.N. resolutions endorsing the U.S.-led war on terrorism.